Precision resistor for non-planar semiconductor device architecture

ABSTRACT

Precision resistors for non-planar semiconductor device architectures are described. In a first example, a semiconductor structure includes first and second semiconductor fins disposed above a substrate. A resistor structure is disposed above the first semiconductor fin but not above the second semiconductor fin. A transistor structure is formed from the second semiconductor fin but not from the first semiconductor fin. In a second example, a semiconductor structure includes first and second semiconductor fins disposed above a substrate. An isolation region is disposed above the substrate, between the first and second semiconductor fins, and at a height less than the first and second semiconductor fins. A resistor structure is disposed above the isolation region but not above the first and second semiconductor fins. First and second transistor structures are formed from the first and second semiconductor fins, respectively.

TECHNICAL FIELD

Embodiments of the invention are in the field of semiconductor devicesand processing and, in particular, precision resistors for non-planarsemiconductor device architectures.

BACKGROUND

For the past several decades, the scaling of features in integratedcircuits has been a driving force behind an ever-growing semiconductorindustry. Scaling to smaller and smaller features enables increaseddensities of functional units on the limited real estate ofsemiconductor chips. For example, shrinking transistor size allows forthe incorporation of an increased number of memory or logic devices on achip, lending to the fabrication of products with increased capacity.The drive for ever-more capacity, however, is not without issue. Thenecessity to optimize the performance of each device becomesincreasingly significant.

In the manufacture of integrated circuit devices, multi-gatetransistors, such as tri-gate transistors, have become more prevalent asdevice dimensions continue to scale down. In conventional processes,tri-gate transistors are generally fabricated on either bulk siliconsubstrates or silicon-on-insulator substrates. In some instances, bulksilicon substrates are preferred due to their lower cost and becausethey enable a less complicated tri-gate fabrication process. In otherinstances, silicon-on-insulator substrates are preferred because of theimproved short-channel behavior of tri-gate transistors.

Scaling multi-gate transistors has not been without consequence,however. As the dimensions of these fundamental building blocks ofmicroelectronic circuitry are reduced and as the sheer number offundamental building blocks fabricated in a given region is increased,the constraints on including passive features among active devices haveincreased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a top angled view and a cross-sectional view of aprecision resistor for a non-planar semiconductor device architecture,in accordance with an embodiment of the present invention.

FIG. 1B illustrates a cross-sectional view of a precision resistor for anon-planar semiconductor device architecture, in accordance with anotherembodiment of the present invention.

FIGS. 2A-2K illustrate cross-sectional views representing variousoperations in a method of fabricating a precision resistor for anon-planar semiconductor device architecture, in accordance with anembodiment of the present invention.

FIGS. 3A-3K illustrate cross-sectional views representing variousoperations in another method of fabricating a precision resistor for anon-planar semiconductor device architecture, in accordance with anembodiment of the present invention.

FIGS. 4A-4L illustrate cross-sectional views representing variousoperations in another method of fabricating a precision resistor for anon-planar semiconductor device architecture, in accordance with anembodiment of the present invention.

FIGS. 5A-5F illustrate cross-sectional views representing variousoperations in another method of fabricating a precision resistor for anon-planar semiconductor device architecture, in accordance with anembodiment of the present invention.

FIGS. 6A-6L illustrate cross-sectional views representing variousoperations in another method of fabricating a precision resistor for anon-planar semiconductor device architecture, in accordance with anembodiment of the present invention.

FIG. 7 is a plot provided to demonstrate the variation of presentlydescribed precision resistors versus their tungsten trench counterparts,in accordance with an embodiment of the present invention.

FIG. 8 illustrates a computing device in accordance with oneimplementation of the invention.

DESCRIPTION OF THE EMBODIMENTS

Precision resistors for non-planar semiconductor device architecturesare described. In the following description, numerous specific detailsare set forth, such as specific integration and material regimes, inorder to provide a thorough understanding of embodiments of the presentinvention. It will be apparent to one skilled in the art thatembodiments of the present invention may be practiced without thesespecific details. In other instances, well-known features, such asintegrated circuit design layouts, are not described in detail in orderto not unnecessarily obscure embodiments of the present invention.Furthermore, it is to be understood that the various embodiments shownin the Figures are illustrative representations and are not necessarilydrawn to scale.

Gate electrodes were initially formed from metal (e.g., aluminum).However, for many technology nodes, a Metal-Oxide-Semiconductor FieldEffect Transistor (MOSFET) had included a gate electrode that wasfabricated from polysilicon so as to permit ion implantation (e.g., tocustomize doping to N- or P-type in the same circuit) and silicidation(to reduce contact resistance). Consequently, a resistor associated withthe MOSFET in a circuit was also fabricated with polysilicon. Aso-called “gate-first” process sequence was universally practiced so asto permit blanket deposition of the polysilicon, plasma etch-definedgate lengths, lightly-doped tip regions, dielectric sidewall spacers,and self-aligned source/drain (i.e., to the gate electrode).

As dimensions of the MOSFET continued to be scaled down in recenttechnology nodes, polysilicon depletion became an increasingly severeproblem. As a result, gate electrodes are now being formed from metalagain. However, gate electrodes are typically no longer formed strictlyfrom aluminum. In order to achieve desired work functions, the gateelectrodes are now usually formed from a transition metal, an alloy oftransition metals, or a transition metal nitride. However, adoption ofthe metal gate also provided advantages to an alternative so-called“gate-last” process. One implementation of the gate-last processinvolved a so-called “replacement gate” process which allowed use ofdifferent metals for the N-FET and P-FET in the circuit. When thematerial in the gate electrode was changed from polysilicon back tometal, the material in the resistor was also changed from polysiliconback to metal. Unfortunately, metal resistors often suffer from highprocess variability and a poor temperature coefficient. Thus, it wouldbe desirable to form the resistor with polysilicon again. However, sucha change causes many challenges in process integration particularly for,e.g., non-planar architectures such as trigate process architectures.

Thus, in accordance with one or more embodiments of the presentinvention, precision polysilicon resistor formation methods onnon-planar trigate high-k/metal gate technologies are described. Bycontrast, other approaches for fabricating resistors for use withtrigate high-k/metal gate technology have included the fabrication oftungsten trench resistors (TCN) and tungsten gate contact resistors(GCN) which may subject to very high variability due to tungstenpolishing processing. Such variability may result in I/O functionalityissues. Tungsten may also exhibit undesired material characteristics andvariation with temperature (e.g., poor temperature coefficients).

Polysilicon resistors used in previous planar oxide/poly gatetechnologies may be a preferred option for precision resistor formation.The integration of the polysilicon and metal-gate material systems,however, is difficult with in a trigate high-k/metal gate processtechnology, e.g., particularly when using a replacement gate processflow. Accordingly, one or more embodiments of the present invention aredirected to an integration scheme for fabricating both planar andnon-planar polysilicon resistors in a non-planar device (e.g., trigate)architecture. One or more, if not all, of the approaches describedherein may be integrated monolithically with a trigate high-k/metal gatetransistor fabrication flow. Such integration may enable exploitation ofsuperior characteristics of precision polysilicon resistors, e.g.,versus tungsten resistors, with improvements in variability reduction,temperature coefficient and voltage coefficient improvements.

A non-planar polysilicon resistor may be included as an embeddedpolysilicon resistor with a non-planar architecture. In an embodiment,reference to a non-planar resistor is used herein to describe a resistorhaving a resistive layer formed over one or more fins protruding from asubstrate. As an example, FIG. 1A illustrates a top angled view and across-sectional view of a precision resistor for a non-planarsemiconductor device architecture, in accordance with an embodiment ofthe present invention.

Referring to both views of FIG. 1A, a semiconductor structure 100includes a substrate 102 (only partially shown) having a non-planardevice 104 and a non-planar resistor 106 formed on an isolation layer103. Non-planar device 104 includes a gate stack 108, e.g., a metalgate/high-k gate dielectric gate stack. The gate stack 108 is formedover a first plurality of fins 110. Non-planar resistor 106 includes anon-planar semiconductor layer 112 formed over a second plurality offins 111. Both devices include spacers 114 and contacts 116.

In an embodiment, the first and second pluralities of fins 110 and 111are formed from a bulk substrate 102, as depicted in FIG. 1A. In onesuch example, bulk substrate 102 and, hence, the pluralities of fins 110and 111 may be composed of a semiconductor material that can withstand amanufacturing process and in which charge can migrate. In an embodiment,bulk substrate 102 is composed of a crystalline silicon,silicon/germanium or germanium layer doped with a charge carrier, suchas but not limited to phosphorus, arsenic, boron or a combinationthereof. In one embodiment, the concentration of silicon atoms in bulksubstrate 102 is greater than 97%. In another embodiment, bulk substrate102 is composed of an epitaxial layer grown atop a distinct crystallinesubstrate, e.g. a silicon epitaxial layer grown atop a boron-doped bulksilicon mono-crystalline substrate. Bulk substrate 102 may alternativelybe composed of a group III-V material. In an embodiment, bulk substrate102 is composed of a III-V material such as, but not limited to, galliumnitride, gallium phosphide, gallium arsenide, indium phosphide, indiumantimonide, indium gallium arsenide, aluminum gallium arsenide, indiumgallium phosphide, or a combination thereof. In one embodiment, bulksubstrate 102 is composed of a III-V material and the charge-carrierdopant impurity atoms are ones such as, but not limited to, carbon,silicon, germanium, oxygen, sulfur, selenium or tellurium. In anembodiment, bulk substrate 102 and, hence, the pluralities of fins 110and 111 is undoped or only lightly doped. In an embodiment, at least aportion of the pluralities of fins 110 and 111 is strained.

Alternatively, the substrate 102 includes an upper epitaxial layer and alower bulk portion, either of which may be composed of a single crystalof a material which may include, but is not limited to, silicon,germanium, silicon-germanium or a III-V compound semiconductor material.An intervening insulator layer composed of a material which may include,but is not limited to, silicon dioxide, silicon nitride or siliconoxy-nitride may be disposed between the upper epitaxial layer and thelower bulk portion.

Isolation layer 103 may be composed of a material suitable to ultimatelyelectrically isolate, or contribute to the isolation of, a permanentgate structure from an underlying bulk substrate. For example, in oneembodiment, the isolation dielectric layer 103 is composed of adielectric material such as, but not limited to, silicon dioxide,silicon oxy-nitride, silicon nitride, or carbon-doped silicon nitride.It is to be understood that a global layer may be formed and thenrecessed to ultimately expose the active portions of the pluralities offins 110 and 111.

In an embodiment, the non-planar device 104 is a non-planar device suchas, but not limited to, a fin-FET or a tri-gate device. In such anembodiment, a semiconducting channel region of the non-planar device 104is composed of or is formed in a three-dimensional body. In one suchembodiment, the gate stack 108 surrounds at least a top surface and apair of sidewalls of the three-dimensional body, as depicted in FIG. 1A.In another embodiment, at least the channel region is made to be adiscrete three-dimensional body, such as in a gate-all-around device. Inone such embodiment, the gate electrode stack 108 completely surroundsthe channel region.

As mentioned above, in an embodiment, the semiconductor devices 104includes a gate stack 108 at least partially surrounding a portion ofthe non-planar device 104. In one such embodiment, gate stack 108includes a gate dielectric layer and a gate electrode layer (not shownindividually). In an embodiment, the gate electrode of gate stack 108 iscomposed of a metal gate and the gate dielectric layer is composed of ahigh-K material. For example, in one embodiment, the gate dielectriclayer is composed of a material such as, but not limited to, hafniumoxide, hafnium oxy-nitride, hafnium silicate, lanthanum oxide, zirconiumoxide, zirconium silicate, tantalum oxide, barium strontium titanate,barium titanate, strontium titanate, yttrium oxide, aluminum oxide, leadscandium tantalum oxide, lead zinc niobate, or a combination thereof.Furthermore, a portion of gate dielectric layer may include a layer ofnative oxide formed from the top few layers of the substrate 102. In anembodiment, the gate dielectric layer is composed of a top high-kportion and a lower portion composed of an oxide of a semiconductormaterial. In one embodiment, the gate dielectric layer is composed of atop portion of hafnium oxide and a bottom portion of silicon dioxide orsilicon oxy-nitride.

In one embodiment, the gate electrode of gate stack 108 is composed of ametal layer such as, but not limited to, metal nitrides, metal carbides,metal silicides, metal aluminides, hafnium, zirconium, titanium,tantalum, aluminum, ruthenium, palladium, platinum, cobalt, nickel orconductive metal oxides. In a specific embodiment, the gate electrode iscomposed of a non-workfunction-setting fill material formed above ametal workfunction-setting layer.

Non-planar resistor 106 includes non-planar semiconductor layer 112 toprovide a precise resistance for resistor 106. In an embodiment, thesemiconductor layer 112 is formed conformal with the plurality of fins111. In one such embodiment, a dielectric layer (not shown) isolates thesemiconductor layer 112 from the plurality of fins 111. In anembodiment, the semiconductor layer 112 is composed of a layer ofpolycrystalline silicon. In one embodiment, the polycrystalline siliconhas a grain size of approximately 20 nanometers. In a specific suchembodiment, the polycrystalline silicon is doped with boron with a doseapproximately in the range of 1E15-1E17 atoms/cm². In an embodiment, thesemiconductor layer 112 has a resistance that is essentially independentof temperature, particularly over the working temperature of thenon-planar resistor 106.

In an embodiment, the spacers 114 are composed of an insulativedielectric material such as, but not limited to, silicon dioxide,silicon oxy-nitride or silicon nitride. In an embodiment, contacts 116are fabricated from a metal species. The metal species may be a puremetal, such as nickel or cobalt, or may be an alloy such as ametal-metal alloy or a metal-semiconductor alloy (e.g., such as asilicide material).

In another aspect, a planar polysilicon resistor may be included with anon-planar architecture. In an embodiment, reference to a planarresistor is used herein to describe a resistor having a resistive layerformed adjacent to, but not over, one or more fins protruding from asubstrate. As an example, FIG. 1B illustrates a cross-sectional view ofa precision resistor for a non-planar semiconductor device architecture,in accordance with another embodiment of the present invention.

Referring to FIG. 1B, a semiconductor structure 150 includes a substrate102 (only partially shown) having a non-planar device 104 and a planarresistor 156 formed on an isolation layer 103. Non-planar device 104includes a gate stack 108, e.g., a metal gate/high-k gate dielectricgate stack. The gate stack 108 is formed over a plurality of fins 110.Planar resistor 156 includes a planar semiconductor layer 162 formedover isolation layer 103. Both devices include spacers 114 and contacts116.

Planar resistor 156 includes planar semiconductor layer 162 to provide aprecise resistance for resistor 156. In an embodiment, the semiconductorlayer 162 is composed of a layer of polycrystalline silicon. In oneembodiment, the polycrystalline silicon has a grain size ofapproximately 20 nanometers. In a specific such embodiment, thepolycrystalline silicon is doped with boron with a dose approximately inthe range of 1E15-1E17 atoms/cm². In an embodiment, the semiconductorlayer 162 has a resistance that is essentially independent oftemperature, particularly over the working temperature of the planarresistor 156. The other features of FIG. 1 b may be composed ofmaterials similar to those described for FIG. 1A.

One or more embodiments of the present invention address suitableproperties of a precision resistor. For example, in an embodiment, aprecision resistor described herein is compatible with current andfuture process technologies, e.g., the precision resistor structuresdetailed are compatible with a trigate high-k/metal gate process flowwhere polysilicon is sacrificial and replaced with a metal gatearchitecture on a non-planar trigate process. In an embodiment, goodresistor characteristics are provided, e.g., a non-planar integrationscheme provides the advantages of larger effective width and length byutilizing the 3-dimensional wafer topology of a trigate process. Hence,a precision resistor fabricated accordingly may provide increasedresistance uniformity and matching characteristics at a given resistorarea. In an embodiment, a polysilicon resistor described herein providesbetter, e.g., reduced, temperature coefficients and voltage coefficientscompared with other types of resistors.

By contrast, previous polysilicon resistors include the BSR (blockingsalicide resistor) which integrates a poly resistor and a poly-gatetransistor, and EPR (embedded poly resistor) which integrates a polyresistor with a planar HiK-metal gate transistor. Unlike the BSR and EPRresistors, precision resistors according to embodiments described hereinmay be fabricated for a non-planar embedded precision polysiliconresistor integration scheme. The approaches for fabrication describedherein may enable a process flow to modularly integrate a polysiliconresistor on a trigate high-k/metal gate technology with minimal processcost.

Described below are multiple approaches to forming precision polysiliconresistors in a high-k/metal gate technology. As an example ofembodiments contemplated herein, the following fabrication methods aredetailed: (1) TPR (Trigate non-planar Poly Resistor+Trigate HKMGtransistor) (a) dual poly deposition resistor, (b) buried hardmaskstacked poly resistor, (c) recessed poly resistor (CPR), (d) selectivelyimplanted poly resistor (NPR), and (2) MPR (masked planar polyresistor+Trigate HKMG transistor).

Regarding approaches of the type (I) above, in an embodiment, aprecision resistor is fabricated from polysilicon material with asilicide connected to a tungsten contact. Features of such integrationschemes include, but are not limited to, (1) polysilicon wraps around arecessed shallow trench isolation (STI) surface and elevated diffusionfin structures to provide larger effective length/width at a given area.The thin and recessed poly on the lower plane (non-planer scheme) maypreserve the polysilicon resistor to be intact after multiple polishprocesses that may be necessary in the HiK-metal gate CMOS process. (2)The preserved poly silicon may be integrated with any suitable silicideprocess to ensure low contact resistance.

In a first fabrication approach, FIGS. 2A-2K illustrate cross-sectionalviews representing various operations in a method of fabricating aprecision resistor for a non-planar semiconductor device architecture,in accordance with an embodiment of the present invention. Referring toFIG. 2A, an isolation layer 202 is formed on a patterned bulk substrate204 and recessed to leave a plurality of fins 206 exposed. A first layerof polysilicon 208 and a silicon nitride hardmask 210 is then formedconformal with the plurality of fins 206, as depicted in FIG. 2B.Although not depicted, an insulating layer may first be formed on fins206 to ultimately insulate polysilicon layer 208 from the fin material.Referring to FIG. 2C, a patterning process, e.g., a lithography and etchprocess, of the first layer of polysilicon 208 and the silicon nitridehardmask 210 is performed to provide a resistor structure 212. A secondlayer of polysilicon 214 is then formed above the resistor structure212. The second layer of polysilicon 214 is planarized, e.g., by achemical mechanical polishing process, and a second hardmask layer 216is formed thereon, as depicted in FIG. 2D. Referring to FIG. 2E, apatterning process, e.g., a lithography and etch process, of the secondlayer of polysilicon 214 and the second hardmask 216 is performed toprovide dummy gate structures 218, which may include spacers 220. Thedummy gate structure 218 may then be masked by mask 222 and an implantprocess 224 is performed to resistor structure 212, as depicted in FIG.2F, e.g., to provide desired resistance characteristics for resistorstructure 212. Referring to FIG. 2G, mask 222 is removed and aninter-layer dielectric layer 226 (e.g., silicon oxide) is formed overthe dummy gate structures 218 and the resistor structure 212. Theinter-layer dielectric layer 226 is planarized to expose the polysiliconof the dummy gate structure 218, but to retain resistor structure 212 asun-exposed. The polysilicon of the dummy gate structures 218 is thenremoved, but the resistor structure 212 is retained, as depicted in FIG.2H. Referring to FIG. 2I, permanent gate electrodes 228, e.g., metalgate electrodes (with, possibly, high-k gate dielectric layers), areformed. Additional inter-layer dielectric material 250 is formed andcontact openings 230 are then formed to expose both the permanent gateelectrodes 228 and the resistor structure 212 for electrical connection,as depicted in FIG. 2J. Although not shown, a silicidation process ofthe polysilicon of the resistor structure may be performed in thecontact openings of the resistor, prior to formation of the contacts.Referring to FIG. 2K, contacts 232 are formed, e.g., by tungsten metalfill and polishing. The permanent gate structures 228 may be gatestructures for a tri-gate device, while the resistor structure 212 maybe a precision polysilicon resistor. The above approach may be referredto as a dual polysilicon deposition approach.

In a second fabrication approach, FIGS. 3A-3K illustrate cross-sectionalviews representing various operations in another method of fabricating aprecision resistor for a non-planar semiconductor device architecture,in accordance with an embodiment of the present invention. Referring toFIG. 3A, an isolation layer 302 is formed on a patterned bulk substrate304 and recessed to leave a plurality of fins 306 exposed. A first layerof polysilicon 308 and a silicon nitride hardmask 310 is then formedconformal with the plurality of fins 306, as depicted in FIG. 3B.Although not depicted, an insulating layer may first be formed on fins306 to ultimately insulate polysilicon layer 308 from the fin material.Referring to FIG. 3C, a patterning process, e.g., a lithography and etchprocess, of the silicon nitride hardmask 310 is performed to provide aresistor mask 311. A second layer of polysilicon 314 is then formedabove the resistor mask 311. The second layer of polysilicon 314 isplanarized, e.g., by a chemical mechanical polishing process, and asecond hardmask layer 316 is formed thereon, as depicted in FIG. 3D.Referring to FIG. 3E, a patterning process, e.g., a lithography and etchprocess, of the first layer of polysilicon 308, the second layer ofpolysilicon 314, and the second hardmask 316 is performed to providedummy gate structures 318, which may include spacers 320, and to provideresistor structure 312. The dummy gate structure 318 may then be maskedby mask 322 and an implant process 324 is performed to resistorstructure 312, as depicted in FIG. 3F, e.g., to provide desiredresistance characteristics for resistor structure 312. Referring to FIG.3G, mask 322 is removed and an inter-layer dielectric layer 326 (e.g.,silicon oxide) is formed over the dummy gate structures 318 and theresistor structure 312. The inter-layer dielectric layer 326 isplanarized to expose the polysilicon of the dummy gate structure 318,but to retain resistor structure 312 as un-exposed. The polysilicon ofthe dummy gate structures 318 is then removed, but the resistorstructure 312 is retained, as depicted in FIG. 3H. Referring to FIG. 3I,permanent gate electrodes 328, e.g., metal gate electrodes (with,possibly, high-k gate dielectric layers), are formed. Additionalinter-layer dielectric material 350 is formed and contact openings 330are then formed to expose both the permanent gate electrodes 328 and theresistor structure 312 for electrical connection, as depicted in FIG.3J. Although not shown, a silicidation process of the polysilicon of theresistor structure may be performed in the contact openings of theresistor, prior to formation of the contacts. Referring to FIG. 3K,contacts 332 are formed, e.g., by tungsten metal fill and polishing. Thepermanent gate structures 328 may be gate structures for a tri-gatedevice, while the resistor structure 312 may be a precision polysiliconresistor. The above approach may be referred to as a buried hardmaskstacked polysilicon resistor approach.

In a third fabrication approach, FIGS. 4A-4L illustrate cross-sectionalviews representing various operations in another method of fabricating aprecision resistor for a non-planar semiconductor device architecture,in accordance with an embodiment of the present invention. Referring toFIG. 4A, an isolation layer 402 is formed on a patterned bulk substrate404 and recessed to leave a plurality of fins 406 exposed. A layer ofpolysilicon 408 is then formed above the fins 406, as depicted in FIG.4B. Although not depicted, an insulating layer may first be formed onfins 406 to ultimately insulate polysilicon layer 408 from the finmaterial. Referring to FIG. 4C, the layer of polysilicon 408 isplanarized, e.g., by a chemical mechanical planarization process, and asilicon nitride hardmask 410 is then formed. A patterning process, e.g.,a lithography and etch process, of the silicon nitride hardmask 410 andthe layer of polysilicon 408 is then performed to provide dummy gatestructures 418 and a resistor structure 412, which may include spacers420, as depicted in FIG. 4D. Referring to FIG. 4E, the dummy gatestructure 418 may then be masked by mask 422. The exposed resistorstructure 412 is then recessed, e.g., by an etch process. The recessing423, in one embodiment, involved removal of the hardmask as well as aportion of the polysilicon layer. An implant process 424 is performed toresistor structure 412, as depicted in FIG. 4F, e.g., to provide desiredresistance characteristics for resistor structure 412. Referring to FIG.4G, mask 422 is removed and an inter-layer dielectric layer 426 (e.g.,silicon oxide) is formed over the dummy gate structures 418 and theresistor structure 412. The inter-layer dielectric layer 426 isplanarized to expose the polysilicon of the dummy gate structure 418,but to retain resistor structure 412 as un-exposed. The polysilicon ofthe dummy gate structures 418 is then removed, but the resistorstructure 412 is retained, as depicted in FIG. 4H. Referring to FIG. 4I,permanent gate electrodes 428, e.g., metal gate electrodes (with,possibly, high-k gate dielectric layers), are formed. Additionalinter-layer dielectric material 450 is then formed, as depicted in FIG.4J. Referring to 4K, contact openings 430 are then formed to expose boththe permanent gate electrodes 428 and the resistor structure 412 forelectrical connection. Although not shown, a silicidation process of thepolysilicon of the resistor structure may be performed in the contactopenings of the resistor, prior to formation of the contacts. Contacts432 are then formed, e.g., by tungsten metal fill and polishing, asdepicted in FIG. 4L. The permanent gate structures 428 may be gatestructures for a tri-gate device, while the resistor structure 412 maybe a precision polysilicon resistor. The above approach may be referredto as a recessed polysilicon resistor approach.

In a fourth fabrication approach, FIGS. 5A-5F illustrate cross-sectionalviews representing various operations in another method of fabricating aprecision resistor for a non-planar semiconductor device architecture,in accordance with an embodiment of the present invention. Referring toFIG. 5A, an isolation layer 502 is formed on a patterned bulk substrate504 with hardmask portions 503 protruding there from. The isolationlayer 502 is recessed to leave a plurality of fins 506 exposed, e.g., ata height of approximately 45 nanometers above the isolation layer 502,as depicted in FIG. 5B. Referring to FIG. 5C, a protective oxide layer507 is formed conformal with the fins 506, e.g., by chemical vapordeposition of a silicon oxide layer. A layer of polysilicon 508 is thenformed above the protective oxide layer 507, as depicted in FIG. 5D. Inone embodiment, the protective oxide layer 507 has a thickness ofapproximately 2.5 nanometers and the layer of polysilicon 508 has athickness of approximately 40 nanometers. Referring to FIG. 5E, aphotoresist layer 560 is formed and patterned above the layer ofpolysilicon 508, leaving exposed a region of the layer of polysilicon508 between fins 506. An implant process 524, such as a high dose p+implant process, is performed to provide a doped polysilicon region 562,as is also depicted in FIG. 5E. Referring to FIG. 5F, the photoresistlayer 560 is removed and the undoped portion of the polysilicon layer508 are removed, e.g., by a selective wet etch process such astetramethylammonium hydroxide (TMAH). The remaining doped polysiliconregion 562 may subsequently be used to form a precision resistor. Theabove approach may be referred to as a selectively implanted polysiliconresistor approach.

Regarding approaches of the type (II) above, in an embodiment, ahardmask is used to modify polish behavior during a poly opening polishto prevent a desired resistor area from being exposed (and,subsequently, removed). The protected polysilicon is then salicided andelectrically connected to source/drain contacts.

In a fifth fabrication approach, FIGS. 6A-6L illustrate cross-sectionalviews representing various operations in another method of fabricating aprecision resistor for a non-planar semiconductor device architecture,in accordance with an embodiment of the present invention. Referring toFIG. 6A, an isolation layer 602 is formed on a patterned bulk substrate604 and recessed to leave a plurality of fins 606 exposed. A layer ofpolysilicon 608 is then formed above the fins 606, as depicted in FIG.6B. Although not depicted, an insulating layer may first be formed onfins 606 to ultimately insulate polysilicon layer 608 from the finmaterial. Referring to FIG. 6C, the layer of polysilicon 608 isplanarized, e.g., by a chemical mechanical planarization process, and asilicon nitride hardmask 610 is then formed. A patterning process, e.g.,a lithography and etch process, of the silicon nitride hardmask 610 andthe layer of polysilicon 608 is then performed to provide dummy gatestructures 618 and a resistor structure 612, which may include spacers620, as depicted in FIG. 6D. Referring to FIG. 6E, the dummy gatestructure 618 may then be masked by mask 622. The exposed resistorstructure 612 is then subjected to an implant process 624, e.g., toprovide desired resistance characteristics for resistor structure 612.Mask 622 is removed and an inter-layer dielectric layer 626 (e.g.,silicon oxide) is formed and planarized over the dummy gate structures618 and the resistor structure 612, as depicted in FIG. 6F. Referring toFIG. 6G, a second hardmask layer 670 is formed and patterned to coverresistor structure 612 but to expose dummy gate structures 618. Thepolysilicon of the dummy gate structures 618 is then removed, but theresistor structure 612 is retained, as depicted in FIG. 6H. Referring toFIG. 6I, permanent gate electrodes 628, e.g., metal gate electrodes(with, possibly, high-k gate dielectric layers), are formed. Additionalinter-layer dielectric material 650 is then formed, as depicted in FIG.6J. Referring to 6K, contact openings 630 are then formed to expose boththe permanent gate electrodes 628 and the resistor structure 612 forelectrical connection. Contacts 632 are then formed, e.g., by tungstenmetal fill and polishing, as depicted in FIG. 6L. Although not shown, asilicidation process of the polysilicon of the resistor structure may beperformed in the contact openings of the resistor, prior to formation ofthe contacts. The permanent gate structures 628 may be gate structuresfor a tri-gate device, while the resistor structure 612 may be aprecision polysilicon resistor.

In the above described approaches, an exposed plurality of dummy gatesmay ultimately be replaced in a replacement gate process scheme. In sucha scheme, dummy gate material such as polysilicon or silicon nitridepillar material, may be removed and replaced with permanent gateelectrode material. In one such embodiment, a permanent gate dielectriclayer is also formed in this process, as opposed to being carriedthrough from earlier processing.

In an embodiment, the plurality of dummy gates is removed by a dry etchor wet etch process. In one embodiment, the plurality of dummy gates iscomposed of polycrystalline silicon or amorphous silicon and is removedwith a dry etch process comprising SF₆. In another embodiment, theplurality of dummy gates is composed of polycrystalline silicon oramorphous silicon and is removed with a wet etch process comprisingaqueous NH₄OH or tetramethylammonium hydroxide. In one embodiment, theplurality of dummy gates is composed of silicon nitride and is removedwith a wet etch comprising aqueous phosphoric acid.

Perhaps more generally, one or more embodiments of the present inventionmay be directed to a gate aligned contact process. Such a process may beimplemented to form contact structures for semiconductor structurefabrication, e.g., for integrated circuit fabrication. In an embodiment,a contact pattern is formed as aligned to an existing gate pattern. Bycontrast, conventional approaches typically involve an additionallithography process with tight registration of a lithographic contactpattern to an existing gate pattern in combination with selectivecontact etches. For example, a conventional process may includepatterning of a poly (gate) grid with separately patterning of contactsand contact plugs.

Referring to FIG. 7, a plot 700 is provided to demonstrate the variationof presently described precision resistors versus their tungsten trenchcounterparts, in accordance with an embodiment. Referring to plot 700,present resistors (EPR) show significantly less resistance variation thetungsten trench resistors (TCN). That is, the resistance variation issubstantially reduced, enabling more accurate and tighter analogdesigns, for the presently described resistors.

Embodiments described herein may be applicable to designs requiring aresistor with a predictable and consistent resistance value. Currenttungsten trench resistors may have large resistance and temperaturevariations, requiring margin to be built into a circuit. By contrast, inan embodiment, precision resistors described herein enable a simpler,smaller circuit design and footprint, along with superior matching andvariability. Such characteristics may be of particular concern to analogcircuit designers. The precision resistor may also be an integralcollateral for system-on-chip (SoC) designers.

FIG. 8 illustrates a computing device 800 in accordance with oneimplementation of the invention. The computing device 800 houses a board802. The board 802 may include a number of components, including but notlimited to a processor 804 and at least one communication chip 806. Theprocessor 804 is physically and electrically coupled to the board 802.In some implementations the at least one communication chip 806 is alsophysically and electrically coupled to the board 802. In furtherimplementations, the communication chip 806 is part of the processor804.

Depending on its applications, computing device 800 may include othercomponents that may or may not be physically and electrically coupled tothe board 802. These other components include, but are not limited to,volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flashmemory, a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth).

The communication chip 806 enables wireless communications for thetransfer of data to and from the computing device 800. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 806 may implement anyof a number of wireless standards or protocols, including but notlimited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE,GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well asany other wireless protocols that are designated as 3G, 4G, 5G, andbeyond. The computing device 800 may include a plurality ofcommunication chips 806. For instance, a first communication chip 806may be dedicated to shorter range wireless communications such as Wi-Fiand Bluetooth and a second communication chip 806 may be dedicated tolonger range wireless communications such as GPS, EDGE, GPRS, CDMA,WiMAX, LTE, Ev-DO, and others.

The processor 804 of the computing device 800 includes an integratedcircuit die packaged within the processor 804. In some implementationsof the invention, the integrated circuit die of the processor includesone or more devices, such as MOS-FET transistors built in accordancewith implementations of the invention. The term “processor” may refer toany device or portion of a device that processes electronic data fromregisters and/or memory to transform that electronic data into otherelectronic data that may be stored in registers and/or memory.

The communication chip 806 also includes an integrated circuit diepackaged within the communication chip 806. In accordance with anotherimplementation of the invention, the integrated circuit die of thecommunication chip includes one or more devices, such as precisionresistors for non-planar semiconductor device architectures built inaccordance with implementations of the invention.

In further implementations, another component housed within thecomputing device 800 may contain an integrated circuit die that includesone or more devices, such as precision resistors for non-planarsemiconductor device architectures built in accordance withimplementations of the invention.

In various implementations, the computing device 800 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, the computingdevice 800 may be any other electronic device that processes data.

Thus, embodiments of the present invention include precision resistorsfor non-planar semiconductor device architectures and methods offabricating precision resistors for non-planar semiconductor devicearchitectures.

In an embodiment, a semiconductor structure includes first and secondsemiconductor fins disposed above a substrate. A resistor structure isdisposed above the first semiconductor fin but not above the secondsemiconductor fin. A transistor structure is formed from the secondsemiconductor fin but not from the first semiconductor fin.

In one embodiment, the resistor structure includes a resistive materiallayer disposed conformal with the first semiconductor fin.

In one embodiment, the resistive material layer is composed ofpolycrystalline silicon.

In one embodiment, the polycrystalline silicon has a grain size ofapproximately 20 nanometers.

In one embodiment, the polycrystalline silicon is doped with boron witha dose approximately in the range of 1E15-1E17 atoms/cm².

In one embodiment, the resistive material layer has a resistance that isessentially independent of temperature over a working temperature rangeof the resistor structure.

In one embodiment, the semiconductor structure further includes anelectrically insulating layer disposed between the resistive materiallayer and the first semiconductor fin.

In one embodiment, the resistor structure includes tungsten metalcontacts coupled to nickel silicide regions disposed in thepolycrystalline silicon.

In one embodiment, the transistor structure includes source and drainregions disposed in the second semiconductor fin, and a gate stackdisposed above the second semiconductor fin, and the gate stack includesa high-k gate dielectric layer and a metal gate electrode.

In one embodiment, the first semiconductor fin is of a first pluralityof semiconductor fins and the second semiconductor fin is of a secondplurality of semiconductor fins, the resistor structure is disposedabove the first plurality of semiconductor fins but not above the secondplurality of semiconductor fins, and the transistor structure is formedfrom the second plurality of semiconductor fins but not from the firstplurality of semiconductor fins.

In one embodiment, the first and second pluralities of semiconductorfins are electrically coupled to an underlying bulk semiconductorsubstrate.

In one embodiment, the resistor structure is a non-planar resistorstructure.

In another embodiment, a semiconductor structure includes first andsecond semiconductor fins disposed above a substrate. An isolationregion is disposed above the substrate, between the first and secondsemiconductor fins, and at a height less than the first and secondsemiconductor fins. A resistor structure is disposed above the isolationregion but not above the first and second semiconductor fins. First andsecond transistor structures are formed from the first and secondsemiconductor fins, respectively.

In one embodiment, the resistor structure includes a resistive materiallayer disposed conformal with the isolation region.

In one embodiment, the resistive material layer is composed ofpolycrystalline silicon.

In one embodiment, the polycrystalline silicon has a grain size ofapproximately 20 nanometers.

In one embodiment, the polycrystalline silicon is doped with boron witha dose approximately in the range of 1E15-1E17 atoms/cm².

In one embodiment, the resistive material layer has a resistance that isessentially independent of temperature over a working temperature rangeof the resistor structure.

In one embodiment, the resistive material layer has a top surface at aheight less than the heights of the first and second semiconductor fins.

In one embodiment, the resistor structure includes tungsten metalcontacts coupled to nickel silicide regions disposed in thepolycrystalline silicon.

In one embodiment, the first and second transistor structures eachincludes source and drain regions disposed in the first or secondsemiconductor fin, respectively, and a gate stack disposed above thefirst and second semiconductor fin, respectively. Each gate stackincludes a high-k gate dielectric layer and a metal gate electrode.

In one embodiment, the first semiconductor fin is of a first pluralityof semiconductor fins and the second semiconductor fin is of a secondplurality of semiconductor fins, and the first transistor structure isformed from the first plurality of semiconductor fins and the secondtransistor structure is formed from the second plurality ofsemiconductor fins.

In one embodiment, the first and second pluralities of semiconductorfins are electrically coupled to an underlying bulk semiconductorsubstrate.

In one embodiment, the resistor structure is a planar resistorstructure.

In an embodiment, a method of fabricating a semiconductor structureincludes forming first and second semiconductor fins above a substrate.The method also includes forming a resistor structure above the firstsemiconductor fin but not above the second semiconductor fin. The methodalso includes forming a transistor structure from the secondsemiconductor fin but not from the first semiconductor fin. Forming thetransistor structure includes forming one or more dummy gates above thesecond semiconductor fin and, subsequent to forming the resistorstructure, replacing the one or more dummy gates with a permanent gatestack.

In one embodiment, forming the resistor structure includes forming aresistive material layer conformal with the first semiconductor fin.

In one embodiment, forming the resistive material layer includes forminga polycrystalline silicon layer having a grain size of approximately 20nanometers.

In an embodiment, a method of fabricating a semiconductor structureincludes forming first and second semiconductor fins above a substrate.The method also includes forming an isolation region above thesubstrate, between the first and second semiconductor fins, and at aheight less than the first and second semiconductor fins. The methodalso includes forming a resistor structure above the isolation regionbut not above the first and second semiconductor fins. The method alsoincludes forming first and second transistor structures from the firstand second semiconductor fins, respectively. Forming the first andsecond transistor structures includes forming one or more dummy gatesabove the first and second semiconductor fins and, subsequent to formingthe resistor structure, replacing the one or more dummy gates with apermanent gate stack.

In one embodiment, forming the resistor structure includes forming aresistive material layer conformal with the isolation region.

In one embodiment, forming the resistive material layer includes forminga polycrystalline silicon layer having a grain size of approximately 20nanometers.

What is claimed is:
 1. A semiconductor structure, comprising: first andsecond semiconductor fins disposed above a substrate; a resistorstructure disposed above the first semiconductor fin but not above thesecond semiconductor fin; and a transistor structure formed from thesecond semiconductor fin but not from the first semiconductor fin. 2.The semiconductor structure of claim 1, wherein the resistor structurecomprises a resistive material layer disposed conformal with the firstsemiconductor fin.
 3. The semiconductor structure of claim 2, whereinthe resistive material layer comprises polycrystalline silicon.
 4. Thesemiconductor structure of claim 3, wherein the polycrystalline siliconhas a grain size of approximately 20 nanometers.
 5. The semiconductorstructure of claim 4, wherein the polycrystalline silicon is doped withboron with a dose approximately in the range of 1E15-1E17 atoms/cm². 6.The semiconductor structure of claim 3, wherein the resistor structurecomprises tungsten metal contacts coupled to nickel silicide regionsdisposed in the polycrystalline silicon.
 7. The semiconductor structureof claim 2, wherein the resistive material layer has a resistance thatis essentially independent of temperature over a working temperaturerange of the resistor structure.
 8. The semiconductor structure of claim2, further comprising: an electrically insulating layer disposed betweenthe resistive material layer and the first semiconductor fin.
 9. Thesemiconductor structure of claim 1, wherein the transistor structurecomprises source and drain regions disposed in the second semiconductorfin, and a gate stack disposed above the second semiconductor fin, andwherein the gate stack comprises a high-k gate dielectric layer and ametal gate electrode.
 10. The semiconductor structure of claim 1,wherein the first semiconductor fin is of a first plurality ofsemiconductor fins and the second semiconductor fin is of a secondplurality of semiconductor fins, wherein the resistor structure isdisposed above the first plurality of semiconductor fins but not abovethe second plurality of semiconductor fins, and wherein the transistorstructure is formed from the second plurality of semiconductor fins butnot from the first plurality of semiconductor fins.
 11. Thesemiconductor structure of claim 10, wherein the first and secondpluralities of semiconductor fins are electrically coupled to anunderlying bulk semiconductor substrate.
 12. The semiconductor structureof claim 1, wherein the resistor structure is a non-planar resistorstructure.
 13. A semiconductor structure, comprising: first and secondsemiconductor fins disposed above a substrate; an isolation regiondisposed above the substrate, between the first and second semiconductorfins, and at a height less than the first and second semiconductor fins;a resistor structure disposed above the isolation region but not abovethe first and second semiconductor fins; and first and second transistorstructures formed from the first and second semiconductor fins,respectively.
 14. The semiconductor structure of claim 13, wherein theresistor structure comprises a resistive material layer disposedconformal with the isolation region.
 15. The semiconductor structure ofclaim 14, wherein the resistive material layer comprises polycrystallinesilicon.
 16. The semiconductor structure of claim 15, wherein thepolycrystalline silicon has a grain size of approximately 20 nanometers.17. The semiconductor structure of claim 16, wherein the polycrystallinesilicon is doped with boron with a dose approximately in the range of1E15-1E17 atoms/cm².
 18. The semiconductor structure of claim 14,wherein the resistive material layer has a resistance that isessentially independent of temperature over a working temperature rangeof the resistor structure.
 19. The semiconductor structure of claim 14,wherein the resistive material layer has a top surface at a height lessthan the heights of the first and second semiconductor fins.
 20. Thesemiconductor structure of claim 15, wherein the resistor structurecomprises tungsten metal contacts coupled to nickel silicide regionsdisposed in the polycrystalline silicon.
 21. The semiconductor structureof claim 13, wherein the first and second transistor structures eachcomprises source and drain regions disposed in the first or secondsemiconductor fin, respectively, and a gate stack disposed above thefirst and second semiconductor fin, respectively, and wherein the gatestack comprises a high-k gate dielectric layer and a metal gateelectrode.
 22. The semiconductor structure of claim 13, wherein thefirst semiconductor fin is of a first plurality of semiconductor finsand the second semiconductor fin is of a second plurality ofsemiconductor fins, and wherein the first transistor structure is formedfrom the first plurality of semiconductor fins and the second transistorstructure is formed from the second plurality of semiconductor fins. 23.The semiconductor structure of claim 22, wherein the first and secondpluralities of semiconductor fins are electrically coupled to anunderlying bulk semiconductor substrate.
 24. The semiconductor structureof claim 13, wherein the resistor structure is a planar resistorstructure.